It is known in the art of designing drive trains for motor vehicles, such as automobiles and trucks, to provide for differential action between driving wheels carried at opposite ends of an axle assembly of the vehicle. Typically, the axle is divided into two segments with inner ends of the separate axle segments splined to drive gears contained within a differential assembly. Conventional differential assemblies of the type commonly used on motor vehicles include two bevel drive gears carried within the differential assembly and mounted on splines formed on the ends of the axle segments which are inserted into the assembly.
Generally, the two axle segments of a differential are aligned on a common center axis of rotation, however, some manufacturers prefer to build in a slight misalignment or "camber" for their axle assemblies. Where it is desirable to provide for slight angular misalignments of the axle segments relative to a common center axis therebetween, it has been the practice, with conventional differential designs, to provide for a clearance between the ends of the axle parts and the housing of the differential assembly so that a certain amount of flexing of the axle ends can be attained.
In contrast with conventional differential assemblies, the differential assembly which is the subject of this invention is of a type that does not utilize bevel gears and is generally of the design shown in U.S. Pat. No. 2,859,641 of Nov. 11, 1958 in the name of Gleasman. This patent is incorporated herein by reference to the extent necessary to provide specific details of a type of differential assembly which does not utilize bevel gears. The patent discloses a mechanism termed a "cross axis compound planetary gear complex". This type of differential includes worm gears, coupled to each axle end as drive gears, together with so called "balancing" or transfer gears associated with each of the worm drive gears and in mesh with each other for transferring and dividing torque between the axle ends. The transfer gears are mounted in pairs, and each transfer gear of a pair rotates on an axis of rotation that is substantially tangental to the pitch of an associated axle drive gear.
One approach for accommodating angular misalignments of axle segments has been to simply provide sufficient space around the ends of the axle segments where they enter the differential assembly to permit a flexing of the axle segments to whatever mounted position is desired for a given axle design. With this arrangement, the bevel drive gears which are carried on the innermost ends of the axle segments are simply tilted slightly with the angular displacement of the turning axes of associated axle segments, and this slight tilt of the drive gears requires some modification of the tooth geometry of the individual drive gears so that they mesh correctly with associated bevel transfer gears within the differential assembly.
In addition to providing for specific means for accommodating angular misalignments of axle segments in a differential having worm-type driving gears, the present invention also solves a problem with respect to providing for a better centering and positioning of each axle segment relative to a differential housing through the use of geometric structures within the housing to accommodate and fix the positions of the axle segments. In addition, it is necessary to consider the effect of angular misalignments of axle segments on any spacer or thrust member which may be positioned between the innermost ends of the axle segments contained within a differential assembly. Accordingly, the present invention provides for a specific geometric relationship between the axle ends and any such spacer member that may be included within the assembly.